Starting in the 1990's, some physicians began to devote all of their time to the care of hospitalized patients. They are referred to as hospitalists. Our preliminary data suggest a rapid growth in the number of hospitalized older patients cared for nationally by hospitalists, from 6.4% in 1995 to 36.3% in 2005. In some areas the majority of inpatients now receive their care from hospitalists. Most of these patients were at community, non- teaching hospitals. To a large extent, this rapid growth and its effect on hospital care has gone unexamined. Almost all prior studies of the hospitalist model have been at single institutions, usually academic medical centers. These studies, including several prospective trials, suggest that hospitalist care is associated with shorter length of stay and lower hospital costs, with no differences in outcomes (usually assessed as hospital or 30 day mortality). However, there have been no national or population-based studies assessing the growth of hospitalists and their impact on the processes and outcomes of hospital care. In particular, it is not at all clear that the results of trials in an academic hospital are generalizable to non-teaching hospitals. Our Specific Aims are: 1. Describe the patterns of growth of hospitalist care in the US from 1995 through 2008. 2. Investigate the effect of hospitalist care on length of stay and hospital and professional charges and assess whether the effect varies by hospital, patient or hospitalist characteristics. 3. Evaluate the effect of hospitalists on general and key diagnosis-specific processes of care and whether these vary by characteristics of the patient, hospital, and hospitalist. 4. Evaluate the impact of hospitalists on outcomes of care, and whether these vary by diagnosis, other patient characteristics, type of hospital, and characteristics of the hospitalist. We will address these aims using a 5% national sample of Medicare charge data from 1995 through 2008. 1 PUBLIC HEALTH RELEVANCE: The last 20 years has seen a steep rise in the number of older patients cared for in hospitals by hospitalists, that is, physicians who devote all their time to care of hospitalized patients. Using Medicare and other data, we will characterize the growth in hospitalist care from 1995-2008, and look at key indicators to evaluate the impact of hospitalists on processes and outcomes of care.